【作者】 张华；

【导师】 陆阳；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2011， 博士

【摘要】 土石堆积层斜坡在我国地震山地灾害较为严重的西南山区分布广泛,就其地震诱导行为的研究对于国民经济建设、保障人民生命财产有重要意义。由于岩土体成因、赋存地质环境、演变历程等的差异,加之地震、降雨、人类工程活动等诸多不确定因素的影响,不同地区土石堆积层斜坡状态不一,各具特点；但是在各个地区,地貌、环境条件等因素相近的前提下,堆积层在扰动下的变形规律及稳定状态存在一定共性。堆积层一般是由第四纪堆积作用形成的土石混合体构成,在与下覆基岩于界面处组成强耦合系统时,两种材料对地震扰动的响应程度有较大的差异,分析时需综合考虑耦合两域各自特性及其相互作用；另一方面,土石混合体作为一种复合体材料,其力学性质受块石级配、形状、土石体积比等因素控制,同时受加载方式、速率、应力水平等影响。针对堆积层边坡的特点,论文在五个方面进行了研究：1)根据四川省地貌与区域环境特征,在对收集到的68处省内公路堆积层边坡信息加以汇总的基础上,将影响边坡稳定的特征因素归结为堆积层厚度、边坡高度、坡率、岩性及其组合、地下水条件、平均年降水量及地震作用等七项指标,进而分别以各项特征因素为参变量,研究其与挡墙、抗滑桩、锚杆、锚索综合、抗滑桩+挡墙及锚杆+挡墙等六类省内公路堆积层边坡典型加固方案之间的统计关系。2)以08年8.30攀枝花6.1级地震对邻近的攀田高速公路望江岭隧道出口堆积层斜坡状态的影响为案例,研究地震作用下堆积层斜坡的变形时效性。在现场连续测斜监测基础上,分析了地震前、后斜坡体深部变形特性及其随时间的演进规律。结果表明,同震顺坡向位移明显,其最大值达到了厘米级,并且顺坡向位移有随深度呈减小的趋势。分析监测数据发现,虽然震后约430天,局部坡体顺坡向位移仍处于调整状态,但主要测孔附近岩土体的时效变形于震后300天左右达到峰值后,已逐渐趋于收敛。综合现场监测成果,可以认为,在经历了大约一年的自适应调整,特别是经09年雨季后,堆积层斜坡已处于整体稳定状态。3)运用平面快速拉格朗日有限差分方法,以地震加速度幅值、频谱特性等为主要参数,分析了地震对望江岭隧道出口堆积层斜坡的扰动。结果表明：(1)输入地震加速度幅值特别是峰值强度的提高不仅对堆积体累积塑性变形具显著影响,且于堆积体稳定状态具有较强的扰动效应；(2)不同地震波动激励下,堆积层斜坡水平位移变化规律较大程度上依赖于所输入动载荷的固有属性；(3)峰值强度为0.49m/s2的Loma Prieta水平地震加速度作用20s末,数值虚拟试验计算结果与现场测斜同震相对位移在量值与分布趋势方面均较为接近。4)考虑到基岩的小变形与堆积体大变形之间差异,论文提出采用有限差分与离散单元外部耦合计算方法研究堆积层斜坡同震响应。首先以支挡结构-填上相互作用实例验证准静态外部耦合算法的有效性,进而将耦合方法由准静态模拟扩展至动力分析,研究地震作用下堆积层斜坡变形规律与动力特性。数值试验中采用平面应变有限差分网格和平行连接圆盘离散元分别模拟下伏基岩与上覆堆积体,界面平滑过渡通过耦合两域取相同时步交替迭代的方法加以实现。动力计算以自重作用下的静力平衡为初始条件,基岩两侧由引入的自由场边界来消除辐射阻尼影响,进而从模型底部输入水平加速度以模拟地震激励。应用上述方法于堆积层斜坡地震响应分析,并对输入地震加速度幅值、持时、频谱特性、堆积体颗粒平行连接强度等相关参数进行了敏感性讨论,结果表明,不同于传统的基于连续介质理论的分析手段,文中采用的连续-离散介质动力耦合算法可描述动载荷作用下堆积体内部细观损伤、分级滑动、表层崩塌等地震灾变的产生、发展全过程。5)论文将坡体概化为花岗岩强风化土与砂土配制而成的匀质土模型,采用土工离心模型试验的方法,探讨地震影响深度为10m时不同震松程度(震松坡体压实系数分为0.90、0.85、0.80)对坡体震后变形与稳定特性的影响,结果表明：(1)随震松坡体损伤程度增大,其应力与位移场于震后短期的调整幅度将相应提高；(2)地震震松坡体密实程度以压实系数表征于0.90-0.80间变化时,其位移场于震后的主要调整时间约为0.7-1.1年；(3)由于物理试验中边坡坡度较缓(约35.7°),地震震松坡体时效位移以竖向固结为主。更多还原

【Abstract】 Slopes covered by deposits are widely distributed in China’s south-western mountainous areas, thus, studies for earthquake induced behaviors of slopes covered by deposits play an important role for both national economic construction and protection of human life and property. Due to othernesses in geological geneses, geological environments and evolution histories of different slope bodies, and also influenced with a good many uncertainties such as earthquakes, rainfalls and artificial activities, slopes covered by deposits in different regions have their own characteristics; in terms of engineering researches, because of the similar landforms and geologic features of the slopes covered by deposits in the same region, there are commonnesses in deformation laws and stability conditions of the slope bodies. From macro perspectives, such a slope could be considered as a strong coupling system that combined deposits and bedrock, responses of the slope to earthquake loads are influenced with behaviors of the two coupling domains and their interactions. On the other hand, deposits could be viewed as a composite material of multi-phases, mechanical property of deposits depends upon factors such as soil-rock volume ratio, and shape and gradation of rubbles, besides, it is influenced by patterns, rates and levels of loads. Based on above mentioned characteristics of slopes covered by deposits, five subjects were studied in this dissertation as follows:1) According to topographic features and regional environments in Sichuan province, characteristic factors interrelated with stabilities of slopes covered by deposits were induced to be the following7indicators:(1) thickness of deposits;(2) height of slope;(3) grade of slope;(4) lithologic association;(5) groundwater condition;(6) average annual precipitation;(7) earthquake effect. And on the basis of gathered information for68slopes covered by deposits of highway in Sichuan province, typical reinforcement schemes are classified into6types:(1) retaining wall;(2) anti-sliding pile;(3) rockbolt;(4) synthetical schemes containing anchor cable;(5) anti-sliding pile+retaining wall;(6) rockbolt+retaining wall. Then, statistical relations between each typical reinforcement schemes and above mentioned characteristic factors were thoroughly discussed.2) In order to further explore aging deformation characteristics of slopes covered by deposits under earthquake loads, a slope covered by deposits of Panzhihua-Tianfang motor way at exit of the Tianfang end of Wangjiangling tunnel is taken as the study object, which is about9.7km from the epicenter of8.30Panzhihua6.1earthquake in2008. On the basis of the continuous borehole inclination monitoring results, coseismic responses and subsequent aging deformation of the slope covered by deposits were investigated. The results show that, the maximum values of coseismic longitudinal displacement for each inclinometer borehole are26to28mm, and the coseismic displacement decreases gradually along with depth. After aging deformation of the slope body near inclinometer boreholes J3and J5reaching the peak value300days after8.30Panzhihua earthquake, it tended to stable condition gradually; But, for inclinometer borehole J1, because of influences of comprehensive factors, its longitudinal displacement was still in the adjusting state430days after8.30Panzhihua earthquake. It is therefore concluded that, by the end of the rainy season in2009, the slope covered by deposits was globally stable.3) Coseismic response rules of the slope covered by deposits were then further studied with the2-D fast Lagrangian finite difference method numerically, and effects of amplitudes and spectrum characteristics of the input horizontal accelerations were also investigated. Simulation results reveal that:(1). Both the cumulative plastic deformation and globe stability condition of the deposits are very sensitive to the amplitude especially the peak value of the input horizontal acceleration;(2). Evolution rules of horizontal displacements of the deposits depend to a great extent on the intrinsic attributes of the earthquake loads;(3). After continuous loadings of the Loma Prieta horizontal acceleration with peak value of0.49m/s2and duration of20s, the coseismic relative longitudinal displacements corresponding to inclinometer borehole J3in the numerical simulation are quite close to the field monitoring results in both the magnitude and distribution pattern.4) Considering of the differences in deformation laws of the deposits and bedrock under earthquake actions, a coupling numerical method that bridging both the finite difference method and discrete element method is introduced in this dissertation. After the applicability of quasi-static analysis of the coupling method being verified with a case study of a shoulder retaining wall acted by soil backfills, the introduced model was extended from quasi-static to dynamic analysis to study deformation rule and dynamic characteristic of the slope covered by deposits subjected to earthquake loads. In the proposed model, the bedrock and deposits are respectively described with the plane-strain finite difference meshes and a collection of parallel bonded rigid disks of DEM. Smooth transition across the continuous and discontinuous domains is obtained by imposing the compatibility condition and equilibrium condition along the interfaces, and the same time step was chosen for the two coupling domains in the iteration procedure. In the course of computation, after the static equilibrium under gravity loads being obtained, dynamic calculation would begin under excitation of horizontal seismic accelerations inputted from the continuum model bottom, and free-field horizontal seismic accelerations inputted from the continuum model bottom, and free-field boundaries were adopted for lateral grids of bedrock meshes to eliminate the radiation damping effect in dynamic calculation. Through above mentioned calculation procedures, dynamic analyses of the slope covered by deposits were conducted, and effects of the relevant parameters such as spectrum characteristics, duration and amplitude of input horizontal acceleration and parallel-bonded strength of the deposits were further investigated. Dynamic coupling numerical results show that, unlike the traditional analysis means based on the continuum theory, with the introduced dynamic coupling method in this dissertation, the whole processes of catastrophes such as meso-damage, multi-stage sliding and surface collapse of the deposits in the earthquake could be studied systematically.5) Three groups of geotechnical centrifuge model tests were conducted to further study the deformation development laws of slope covered by deposits after earthquake actions. Slope bodies were generalized into fabricated soil (mixed with weathered granite soil and sandy soil) models, and influence depth of earthquake to the slope was taken as10m, then, effects of loose degrees of the earthquake loosed slope body on aging deformation and long-term stability of the slope were investigated. The following conclusions could be drawn from analyses:(1). With development of damage extents of the earthquake loosed slope body, adjustment extents of the stress/strain fields in the short term after the earthquake increased accordingly;(2). As compaction coefficients of the earthquake loosed slope body vary from0.90to0.80, the main adjusting time of the slope’s displacement field after the earthquake lies within0.7-1.1years;(3). In the tests, because of the gentle gradient of the slope (35.7°), aging displacments of the slope bodies are domindated with the vertical consolidation.更多还原